Idle at 1000rpms

[frank1966]

Hello all,
I notice my engine likes to idle at 1000 rpms, that is high, we should be ay 750? when I turn it down to 750 it idles a little rough, some shaking. I hooked up a vacuum gauge, its perfect in the green, not sure about the readings, the outside numbers say 50 and the inside numbers say 20 which falls right in the middle of normal operation. The needle is steady at 1000 but not so steady at 750. I'm not sure what to set first, timing, mixing screws or idle screw. All of this is after it comes off the fast idle cam.

[XH29N0G]

Is it a stock build, or something else?  I set my idle higher, just to move the oil around (don't know if that matters).  I have an aftermarket cam so it also does not have vacuum and is lumpy, but I also found that if I advanced my timing and set my idle fuel mixture to where vaccum was highest, that it would idle much more smoothly and at lower RPM.

So my guess, if it is stock, is that it could be the tune up (fuel mixture or timing) or it is just going to be a little rough.  Even with the stock cam, mine didn't idle like a typical small cam engine.  See what others say.

[frank1966]

thanks, its stock I think, it was rebuilt. It smoothes out nicely at 1000. I don't know how to set the timing the correct way I just used my vacuum gauge and moved the distributor around a little until the needle landed in the middle of the gauge where it says normal operation.

[XH29N0G]

What I was advised for setting the timing with the aftermarket cam, was to advance the timing while watching the vacuum gauge (and adjusting the idle as necessary) to set it to the highest vacuum reading.  The catch is that I then had to recurve the distributor so that the total advance was not too high. 

If someone else does not answer here, I suggest looking through the posts for recommendations on setting the total timing for your engine.  Looking through the factory service manual, I see recommended timing of TDC for manual,  2.5 before TDC for auto, and 5 Before TDC for 3-2.  I do not know where this puts the total timing.  My guess is that these are fairly conservative settings and you could advance the timing from these settings.  My other guess is that you will probably be able to advance the total timing.  How much will depend on factors like your compression and the cam. 

If you don't find anything in the posts and no one answers here, I suggest starting a new thread to ask for recommendations on setting the timing with your particular engine.  As you know by now, there is a lot of knowledge here, and more than one person will be able to tell you close to an exact setting, if not exact, for your particular combination.

Good luck with this. 

Also, I assume your ignition and plug wires are in top condition.  I had a rough idle and it was how the old ignition was set (points, gap, and dwell)  I do not know if many still have points. 

[frank1966]

Thanks, all new wires MSD distributor all in one. Should I turn the distributor until I get max vac and rpms then set the mixing screws then the idler screw? Light timing I cant do yet, need to learn how to do that.

[XH29N0G]

I would wait to change the timing from the factory setting until someone else responds and gives specific information.

By Light timing, Do you mean using a timing light?  It is not difficult.  The light is hooked to the battery and the ones today have an inductive clip that goes on the #1 plug wire.  Then it is pointed down toward a tab on the front of the engine by the harmonic balancer.  It will flash when the #1 plug fires and you will see a line that lines up with the tab.  I think your tab should look like the picture I pulled off the web (below), and the zero is where the hole is.  This one has a tape with numbers on the harmonic balancer.  Typically, those numbers are not there, but there is a single line for reference.  If you set it 5 degrees before top dead center, the line on the harmonic balancer would line up with the 5 degree mark just below (on the picture) the little hole in the tab.

I think you set the timing at 850 RPM and you also need to disconnect any vacuum advance settings.